Such a method is known from DE 195 18 914 A1. In order to be able to detect a tiring of a driver of an automobile and the effects as to perception and reaction related thereto, this publication suggests mounting a “multi-contact band” on the steering wheel of the motor vehicle, which comprises numerous individual switches. If none of the switches is pressed by the user during a specific time span, a warning signal sounds. In this known arrangement, the user is therefore compelled to actively press a switch at specific intervals. Otherwise, he will be “awakened” by a warning signal, for example, by a horn device.
JP 4183439 A1 further discloses an arrangement wherein electrodes are mounted on the steering wheel. If the driver touches the steering wheel in the region of the electrodes, then an electrocardiogram is generated. From the evaluation of the electrocardiogram, a reduced alertness or a falling-asleep of the driver are detected.
The known methods have, however, various disadvantages. With a contact band, for example, a check of the alertness of the driver and the position of his hands on the steering wheel is possible only at time intervals, but not continuously. An electrocardiogram, in turn, requires an electric contact between hand and steering wheel which is often not present. Modern vehicles in ever increasing numbers include systems which support the driver while steering the vehicle or support the driver in special driving maneuvers. In these systems, it is necessary for reasons of safety that the driver has his hands tightly on the steering wheel in such a manner that he always has full control over the vehicle and the responsibility for the steering of the vehicle. In the case of an automatic steering support, this is also necessary when, for a time (like when driving straight ahead), no steering intervention by the driver is necessary.